Prostaglandin E2 (PGE2) is involved in inflammation, pain, pyrexia, and the like by means of PGE receptors, and can suppress the PGE2 production to suppress inflammation. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) in the upstream of the prostaglandin biosynthesis pathway, and thereby exhibit anti-inflammatory activity. However, they totally suppress the prostaglandin biosynthesis pathway downstream from the prostanoid production in which COX is involved, and therefore they cause gastric mucosal injury as side effects due to suppression of secretion of gastric mucus or blood flow in gastric mucosa.
There are two types of isozymes of COX, COX-1 and COX-2. Among them, COX-2 is expressed and induced in inflammatory tissues by various inflammation-promoting stimuli (for example, those of cytokines such as interleukin-1β). Medicaments that selectively inhibit this COX-2 suppress the production of PGI2, which has vasodilatation and platelet aggregation actions; however, since they do not inhibit the production of thromboxane A2 (TXA2) catalyzed by COX-1 (TXA2 causes vasoconstriction and platelet coagulation), they are considered to increase risk of thrombosis, and increase cardiovascular events, either.
In the downstream of the biosynthesis pathway of PGE2, PGE2 is biosynthesized from PGH2 by the prostaglandin E synthase (PGE synthase, PGES). As PGES, there are three kinds of enzymes, mPGES-1 (microsomal prostaglandin E2 synthase-1), mPGES-2 (microsomal prostaglandin E2 synthase-2), and cPGES (cytosolic PGE synthase). Among them, mPGES-1 is an inducible trimer enzyme, of which expression is increased by inflammatory stimuli (Proc. Natl. Acad. Sci. USA, 96, pp. 7220-7225, 1999), and it is known to participate in cancer, inflammation, pain, pyrexia, tissue repair, and the like.
Since mPGES-1 inhibitors can selectively inhibit the final step of the PGE2 biosynthesis pathway in inflammation lesions (Pharmacol. Rev., 59, pp. 207-224, 2007; J. Biol. Chem., 279, pp. 33684-33695, 2004), they are expected as anti-inflammatory agents that do not cause gastric mucosal injuries, unlike the non-steroidal anti-inflammatory agents. There are also expected efficacies of mPGES-1 inhibitors for prophylactic and/or therapeutic treatment of pain, rheumatism, osteoarthritis, pyrexia, Alzheimer's disease, multiple sclerosis, arteriosclerosis, ocular hypertension such as glaucoma, ischemic retinopathy, systemic scleroderma, malignant tumors such as large intestine tumor, and diseases for which suppression of the PGE2 production exhibits efficacy (refer to International Patent Publication WO2015/125842 for PGE2, PGES, and mPGES-1, as well as uses of mPGES-1 inhibitors, and the like). In addition, it is also known that mPGES-1 inhibitors increase productions of other prostanoids in connection with the suppression of the PGE2 production (J. Biol. Chem., 280, pp. 16579-16585, 2005).
As such mPGES-1 inhibitors, there are known the heterocyclic derivatives disclosed in Japanese Patent No. 5601422, the substituted pyrimidine compounds disclosed in International Patent Publication WO2015/59618, the triazine compounds disclosed in International Patent Publication WO2015/125842, and the like. International Patent Publication WO2015/59618 discloses a pyrimidine compound substituted with p-trifluoromethylphenyl group and 2-chloro-5-isobutyramidobenzyl group (Example 2), and International Patent Publication WO2015/125842 discloses triazine compounds substituted with p-trifluoromethylphenyl group and 2-chloro-5-isobutyramidobenzyl group (Examples 1 to 28).